Posted
by
timothyon Saturday July 19, 2008 @11:06PM
from the grassy-knollers-know-it's-easy-to-blame dept.

Statesman writes "The Los Angeles Times reports that an Arizona crime lab technician found two felons with remarkably similar genetic profiles, so similar that they would ordinarily be accepted in court as a match, but one felon was black and the other white. The FBI estimated the odds of unrelated people sharing those genetic markers to be as remote as 1 in 113 billion. Dozens of similar matches have been found, and these findings raise questions about the accuracy of the FBI's DNA statistics. Scientists and legal experts want to test the accuracy of official statistics using the nearly 6 million profiles in CODIS, the national system that includes most state and local databases. The FBI has tried to block distribution of the Arizona results and is blocking people from performing similar searches using CODIS. A legal fight is brewing over whether the nation's genetic databases ought to be opened to wider scrutiny. At stake is the credibility of the odds often cited in DNA cases, which can suggest an all but certain link between a suspect and a crime scene."

What we're seeing here is a crack in the government's facade of fake-goodness. The ideas we're fed are that justice is blind, which means (we're taught), ultimately fair; that prosecutors and judges and the legal system in general have our best interests at heart, and so on, platitude after platitude...

But the truth peers 'round the corner here. They're not interested in accuracy, else they'd be all for determining how well this works, or not. The process and the results would both be open. What they're interested in are convictions, because that's how they keep score. That's how the public is keeping score.

This is unfair and irresponsible on two fronts. First, if you get the wrong person for any reason (including using DNA evidence that is supposed to be basically infallible, but is, in fact, fallible); then you've done a wrong to that person, of course. But secondly, for every false conviction the prosecutor and their accomplices notch into their pistols, the real criminal is now completely free -- the case is closed. They're not even looking.

As a society, we need to stop trying to raise up any part of the system based upon count of arrests, convictions, tickets, etc. The temptation to go for easy answers is too high; obviously, if the FBI itself is victim to this, an organization that prides itself on its organizational integrity, groups that have less tradition of trying to do right -- like the local cops who broke down your neighbors door last week -- are going to fall even more prey to such pressures.

As we see that the FBI tries to prevent the truth from coming out about a tool that is less effective than they claim, as they try to prevent exonerating information from reaching the defense, we see true colors.

These people are not our defenders; they claim to be, but they have their own agenda, and it is not about fairness. They're simply counting scalps.

It is hard to believe the FBI won't do the study to get real numbers, but we've been here before. These are the same people who presented bullet lead evidence with equal certainty. The science is impressive but it means nothing when your original premise is wrong. In the bullet lead case, it turns out that matches were common and single boxes often had differences. The coincidence between two people is good reason to review the data and make sure DNA statistics are correct. Until that is done, the odds of DNA matches should be looked on with great skepticism.

It's screw ups like this that make the death penalty a bad idea. While life in prison is a terrible punishment, perhaps more cruel than death, it gives the state a chance to fix its mistakes.

Encouraged, Barlow subpoenaed a new search of the Arizona database. Among about 65,000 felons, there were 122 pairs that matched at nine of 13 loci. Twenty pairs matched at 10 loci. One matched at 11 and one at 12, though both later proved to belong to relatives.

That's about a 1/500 chance of a random match, good evidence but not the 1/1E12 claimed. The FBI needs to get off it's extrapolation and study the data.

What's really threatened is Big Brother's DNA database. If the evidence is not conclusive, th

Well, I'd argue it's not the only reason death is a bad idea. Ghosts don't do a very good job at restitution, for starters, and that's ignoring all the ethical arguments. But you're absolutely correct that whilst the probability of error is indeterminate (well, nobody's being allowed to validate the database) and quite possibly excessive (there are currently one million SNPs tested at deCODEme, not sure how many SNPs or markers are looked at by the FBI - assuming they're that sophisticated and aren't just u

It's screw ups like this that make the death penalty a bad idea. While life in prison is a terrible punishment, perhaps more cruel than death, it gives the state a chance to fix its mistakes.

Falsely sending a person to prison cannot be 'fixed', only perhaps ameliorated. The frequent unfunny jokes about homosexual rape in prison show that not only the conviction system is out of control, but the punishment system is as well.

As a juror it's not clear to me how I'm *ever* supposed to avoid having reasonable doubt. It's very well-established that the reliability of eye witness testimony is terrible. As a chemist, I've always been partial to forensic evidence. But now apparently there's a substantial chance that even quantitative forensics tests like DNA analysis, bullet lead analysis, or fingerprints are bullshit. So what's left? Even with an advanced degree in chemistry, I'm not likely to be able to research and evaluate a forensic procedure well enough to know if the prosecutor and/or lab technicians aren't pulling some sort of shenanigans. In the past I would have been inclined to simply assume that an established forensic procedure was trustworthy, but now that clearly isn't the case.

The findings in CODIS are truly staggering! While the odds of a false match are supposed to be only 1 in 113 BILLION, a search over only 65,000 records turned up 122 matches! About 1 in 533!!

That's not a little glitch or merely "surprising", that's the difference between a match meaning you are 100% the person who was there to you are one of the 7500 residents of a decent sized metro area who might have been there! Further, you're one in half a million in the U.S. who might have been there. One in 12 million worldwide.

It also means that every conviction ever made primarily on the strength of DNA evidence must now be reviewed and even re-tried if justice is at all a consideration.

While, given that this is a metric crapload of egg on the FBI's face, I can understand why they wouldn't want this to be true, if justice was anywhere at all within their objectives, they'd be all for further testing. They'd also want a moratorium on DNA based convictions while they sort this out.

The attempts by the FBI to explain this away based on the way the data was searched sound like desperation. They try to make it sound like this finding is an artifact of the search methodology rather than genuine collisions. They are right that this actually represents 4 billion searches, but even if so, that should provide a 1 in 25 chance of a single match according to the figures they claim. Instead, we have 122 matches. Calling those 4 billion comparisons searches is disingenuous however, any search on the Arizona database would be 65,000 comparisons.

Their rather heavy handed attempts to block all further research are simply inexcusable. It tells me that in spite of their weak excuses, they are well aware of just how damning this actually is.

The upshot of all of this is that DNA is best used as EXCLUSIONARY evidence. If you don't match, it wasn't you period. If you do, it MAY have been you. It's a good way to narrow down a list of suspects or even come up with a list to examine closer (it may or may not be enough by itself to be probable cause).

If there's additional evidence, it may add up to beyond reasonable doubt.

It bears repeating: If the FBI had any interest whatsoever in justice, they'd be the first to examine this more closely. If the DOJ had any interest in justice whatsoever, it would insist that they do it now.

one of the key witnesses for the OJ trial, I forget his name, had said that DNA was a great tool for excluding suspects BUT not good enough to ID them. He was a noble prize winner for his work inventing PCR dna tech. Of course everyone dismissed him at the time as a hired gun for OJ, I guess he gets the last laugh today!

Try a geographic breakdown. Here's a hint: it correlates *strongly* with population density. A very disproportionately high percentage of the crime occurs in the urban areas. Something like 90% of the crime, and 99% of violent crime, in the big urban areas that house about 40% of the population.

I recommend you read a book like Sense and Nonsense About Crime and Drugs [amazon.com]. Our justice system is biased from the top down. For an example, the percentage of black and white drug users is exactly the same; last I read around 13%. However, a minority is more likely to be searched during routine police encounters by the police, more likely to be arrested, more likely to be tried, more likely to be convicted, and more likely to be sentenced to jail time. So, we go from equivalent percentages of black and white drug users to a wildly overrepresented percentage of black inmates on drug offenses; last I read 58%. Also consider that law enforcement often takes a "containment" approach to drug enforcement. To paraphrase a Chris Rock joke, if a 14 year old can score weed you think the cops don't know where the drug dealers are, too?

Oh ye of little experience. You actually believe the cops are so squeaky clean, do you? Corruption permeates much more deeply than you apparently believe. And you don't seem to understand the resources needed to prove one's innocence, instead of pleading it down. That there will make you a statistic. For shame!

There are several "layers" of causality that you have to get through from "population of random 100k people of certain race" to "locked in jail".

Asserting that the only causality is some sort of discrimination without also examining the other layers is just plain old intellectual dishonesty.

Being targeted or not, if you don't do the crime it's pretty hard to end up in jail. Overall society's expectations are pretty clear, even in the depths of whatever crap-ghetto culture you came from. Everybody knows if y

Your statement flies in the face of the call for equal protection under the law. It is not wise to try to justify the outrageous situation we are under. To deny the inherent racism and classism is much worse than intellectual dishonesty. I hope that's not what you are doing.

Ok, continuing with your unprovable premise, perhaps the blacks are just not as smart and tend to get caught more?

Anyone that sees the 'lopsided' amount of black people in prison compared to white really needs their head examined. There is no sinister conspiracy involved here, its just how the chips are falling, for whatever reason.

what is really shocking here, is that these 'matches' were being found in arizona, which has less than 2% of the Us population, unless a lot of other places outsource DNA testing to arizona it suggests that DNA fingerprints are little better than regular fingerprints.

TFA isn't very clear, except that she was working for the state of arizona when she noticed 'identical' matches.

some might suggest that some of the DNA used to identify criminals may have impacts on that persons likelihood to turn to crime.. but we really don't understand much of how the brain works or the effects of slight variations in dna on that.

Possibly significant in terms of sample size.
If person A has a DNA profile that matches one other person in the country, it is still very strong evidence.
If upon checking the other states there was found to be an average of one matching person per state, 50 matches, still strong evidence, but not nearly so conclusive. Would now require stronger supporting evidence to be "beyond reasonable doubt".
If (prison population being approx 1%) there are found to be 100 matches per state, 5000 matches, then DNA becomes more useful as evidence for aquittal than for conviction, ie: non-matching still proves it wasn't you but matching doesn't prove it was you.

Alas, there were 122 matches on 9 loci found in a database of 65000 records (1 in 500) in a single state. There were 20 matches on 10 loci. The matches at 11 and 12 were eliminated because the pairs turned out to be related.

Note that 9 loci are considered "adequate" by "experts".

The figures suggest that if everyone was in the database, we could expect 7500 matches on a search restricted to a decent sized metro area.

I agree that DNA evidence should be considered exclusionary. At most, it could suggest suspec

Yes, but regular fingerprints are actually very good. That's why it's called "DNA fingerprints" and not "DNA shoeprints" or "DNA ballistics evidence".

Brandon Mayfield might disagree. Had he not been able to prove beyond a shadow of doubt (as in hundreds of eyewitnesses) that he was in Portland, Oregon when the FBI said he was killing people in Spain, he would have been in a peck of trouble.

Note the closing sentence of the following story: "an FBI fingerprint examiner told an expert hired by Mayfield the original print no longer exists".

Anyone with skill and with a true criminal mindset (as in, REAL criminals with an axe to grind) will be able to fool the feds. As far as I understand, they're no different than the KGB... they have to present a list of victims... AHEM... "apprehended criminals" in order to justify their existence.

Nothing new. They'll keep criminalizing innocent, harmless things and letting real criminals go. The prison industry is bigger than Chinese outsourcing, but you won't hear about it on CNN or even on the alternative news sites. Nobody wants to mention that outsourcing to China is no different in any aspect than outsourcing government furniture (just an example) to prison labor, which undercuts even the Chinese commies on price. Why do you think they are letting out violent felons while taking in white collar boys for shit crimes nobody cares about? Exactly... a violent felon is a liability to a budding industrial power (aka... the new forced labor camps called "corrections facilities"). A meek and easily subdued white collar boy, well he's easy to walk all over and he's afraid of his fellow inmates AND the guards. He'll do as he's told. Why risk angry violent felons incarcerated with the very profitable and nonviolent white collar "criminals" ?

Bingo. You've said it well chief, but missed the "profit" motive, which is what existed under communism, it existed under socialism, under fascism and in this fascist/socialist hybrid system that we have here in America. Nothing new... just different masks on the same old faces.

I've noticed something: government conspiracies always get modded up here and are usually based on "Think about it. You know it's true, man."

The reason overly pessimistic posts about the government get modded up and not overly optimistic ones seems to be that your average slashdotter is insecure and doesn't want to get lauged at for being naive.

Well call me naive, but I don't think things like this are driven by greed so much as incompetence, hubris, and an "us vs them" mindset.

I do know where you're coming from, and I'd certainly hate to be considered a conspiracy nut. I do try to liberally apply the idiom "never attribute to malice what can be adequately explained by incompetence".

All that said, however, I'm not really seeing a reason here that can be explained by simple incompetence. If they are, at heart, good people, then they would want to know how accurate DNA results are. It wouldn't even expose them to looking bad if it turned out that they'd been using bad evidence - all they'd need to save face would be a photo of an FBI agent shaking hands with someone in a lab coat and a press release explaining how grateful they are for having this weakness in the testing system found. Any other ideas on why they'd want this not to be looked into?

It's human nature not to want to admit mistakes, even to yourself. These people have spent years convicting people on DNA, and in the mind of the public it's rock solid -- if they have you on DNA, case closed.

The upheaval in the court system will be huge. All cases where DNA evidence was used will have to be retried. Throw in the mentality of "we know he's guilty anyways" based on other evidence, and it's not surprising that the FBI would rather sweep this under the carpet.

The idea that the FBI is part of some conspiracy to get slave labor is absurd.

1/113 billion chance a particular person has the same DNA profile as me. 6 million records. So I have a 6 million / 113 billion chance of matching someone else in the database. Drop some zeros and thats 6/113,000. Of course, each of the 6 million people in the database has a the same chance of matching someone - so that's 6/113,000*6,000,000 - which means there should be 318 people who match someone else in CODIS, or 159 'matches'.

# of people matching = size of group * size of group * chance of match

Anytime you have something that has a small chance of matching, but a fairly large sampling group, your chances of matching are high, because your chances of a match existing within the group is the SQUARE of the group size.

So it would be surprising if there were NOT people who matched in CODIS. The question is, are there more or less that 318 of them, and how much more or less?

The other question is: since the database was started, our ability to study DNA, examine genetic markers and recognize which areas are better for identifying individuals has drastically improved. Has the database improved to match this knowledge, or are we relying on outmoded methods? If the former, then it's as good as it is going to get - for now. If the latter, the probability of a false positive could be massively slashed. That would surely be desirable for a crime-fighting system... wouldn't it?

I don't think they are even using markers. I thought they were using a process that basically duplicates the DNA a massive number of times, then use gravity vs. capillary action to weigh the different chromosomes which may or may not have been through a blender 1st. They are not comparing gigabits of data to verify a DNA match.

So what you are saying is that a new sample has a 1 in 19,000 chance (6e6/1.13e11) of finding a match in CODIS at random, even though this is a new sample not present in the database. With thousands of police departments nationwide running samples against CODIS every week, false matches like this may occur frequently. If the consequence is that an innocent person is charged or even convicted of rape or murder, this is frightening.

There is a big difference between telling a lay jury "this match had a one in a 113 billion chance of occurring at random" versus "this is an event that occurs randomly on a routine basis." Non-statisticians have a hard time getting their head around the concept of correction for multiple hypothesis testing.

The real problem is that the FBI match criteria were developed years ago when the CODIS database was small compared to its current size, and these criteria have not been updated in light of growth in the database and new technology. Using state-of-the-art genotyping technology, it should be possible to design a test with a small chance of a false positive match even if the database contained the entire US population.

This would be true, but not everyone who matches is going to be able to have committed the crime. For example, a lot of the people who are in the Database are in prison. That is a pretty good alibi. Many of the people are going to be so far away geographically from the crime committed that they will be dismissed as suspects after cursory investigation. The odds of a false positive get MUCH smaller require that the false positive sample in CODIS must come from someone who is close enough to the crime sce

>>There is a big difference between telling a lay jury "this match had a one in a 113 billion chance of occurring at random" versus "this is an event that occurs randomly on a routine basis." Non-statisticians have a hard time getting their head around the concept of correction for multiple hypothesis testing.

To give an apocryphal quote by Mark Twain: "People use statistics the same way drunks use lampposts - for support, not illumination."

The lack of ability to reason statistically is extremely common in America. I mean extremely common - even in grad students publishing papers on stats, or in the technologically literate crowd. I'd used to write examples of egregiously bad stats in my livejournal in papers and news reports, but gave up because it was so common.

The DNA testing example is actually an example we studied in the Bayseian/conditional chapter of my stats textbook. It described an actual court case in LA where I got was convicted solely by DNA evidence (there was no other evidence to convict him, and he wasn't lucky enough to have an alibi) because the prosecutor confused the odds that (in this case) the odds of the match randomly matching being only one-in-a-million, and those are some pretty powerful odds. Of course, that would mean that in LA alone, there would be 6 people (on average) matching the DNA, and so the chance of the guy being guilty is actually only 1/6 or so.

The problem I have with the DNA "this has a one in 113 billion chance of matching" is that this is an extrapolated number based on certain premises of independence between the different loci. Whereas the more we learn about DNA, the more we learn that there is a high degree of covariability, certainly enough that (as the article shows), the odds of a match are actually much much higher.

The test would immediately give a 100% result of it as non-human DNA.One of the reasons for that is the fact that humans have 23 pairs of chromosomes whereas chimps and other primates have 24 pairs. We didn't "lose" a chromosome - one strand of DNA got glued on to the end of one of the other strands of DNA, so all of the same genetic information is still there.

It's probably even worse than the naive math indicates, because odds are not everybody involved will actually be unrelated in the mathematical sense anymore.

On the other hand... as others point out, in the birthday paradox there's a huge difference between two people have the same birthday and someone has the same birthday as me. However, in a prosecution situation, it is the latter that matters, not the former. Simply showing that the birthday paradox applies doesn't really prove that for a given criminal, that the odds are high that the match is a false positive.

This is also why government attempts (by well meaning people) to simple run dragnets over large datasets looking for "bad people" need to be resisted; while the birthday paradox is not always in play, similar statistical effects can be found in many other situations that cause enormous amounts of false positives. "Due process", where we investigate someone with all available tools only after we already have good reason to suspect them (to simplify, of course), turns out to be important not just for our rights in the abstract, but statistically sound, as well.

At the risk of potentially defending the government (pause for the shocked intake of breath), I find it quite plausible that the government knows all of this, and is resisting this investigation because they do not look forward to explaining this to every jury unto the end of time. While I support open disclosure and letting the chips fall where they may as a matter of principle, if you take a moment to look at this from their point of view, even if you dare take the step of assuming they're not actually out to get you personally (pause for another shocked breath), you might find it hard to avoid having a little sympathy for their position. (If you're still having a hard time, engage the "Most jury members sure are dumb, ha-ha!" cynicism circuit and consider the implications.)

. That is to say, the chance of having marker A might be 1% and the chance of having marker B might be 5%, but the chance of having BOTH might very well be higher (or lower) than.05%.

IANAFG (I am not a forensic geneticist) but the co-segregation of genetic markers is such a fundamental and well understood process that I would have a hard time believing that they wouldn't know and correct for the rates of their chosen set when calculating the probabilities of a matched set.

Of course the statistics they calculate are probably based on estimates of pairwise segregation. Some higher-order effects may be at work that change the statistics relative to a basic model like independent pairwise segregation.

For example, allele A of gene 1 and allele B of gene 2 may not segregate according to a previously measured pairwise stastistic in the presence of allele C of gene 3. Such higher-order effects may have a significant impact on the statistics but would require a *lot* of data to reveal.

I would have a hard time believing that they wouldn't know and correct for the rates of their chosen set when calculating the probabilities of a matched set.

And I would have a hard time believing that the prosecution gives a damn whether what they present is accurate as long as they can get the conviction. I have yet to see a prosecutor in real life who's more concerned with finding the truth than getting the conviction.

1/113 billion chance a particular person has the same DNA profile as me. 6 million records. So I have a 6 million / 113 billion chance of matching someone else in the database.

Forgive me, because I have just come home from the bars (insert joke about me coming home to/. instead of a lady), but wouldn't this only be true if every single profile were the same? You seem to be discounting the matching algorithm altogether and assuming matches are purely random. Or am I missing something?

Glad to see mention of the birthday paradox, it illustrates the issue nicely. I worked on a genetic mark recapture program that encountered just this effect. Initially things looked great but as the sample size increased we started encountering "shadows" (individuals that share markers at all loci sampled but aren't true matches) with greater frequency. To study large populations you need markers with significantly lower probability of identity than has been assumed in a lot of research. We often remarked how rediculous the statistics quoted by journalists and in court are.

THE ISSUES SURROUNDING genetic information in trials may soon become more complicated. The next likely controversy will concern the science of population genetics. Even if a combination of markers is rare among all people, it might appear at higher rates in some ethnic subgroups, says Conrad Gilliam, professor of genetics and development at Columbia. He testified in the 1990 case Castro v. New York State, the first in which a prosecution's attempted use of DNA data was thrown out by the court.

Suppose a murder is committed in Chinatown, Gilliam conjectures, and the police find blood samples. Certain polymorphic variants that occur frequently in Chinese people are rare in Caucasians. If these markers show up in the sample, and the police produce a Chinese suspect, a prosecutor could try to use the DNA as further evidence against him. "However," Gilliam says, "a defense attorney could argue that there could be so many local suspects with the same profile that the evidence has no bearing on the case."

If the markers were truly independent, the polymorphic variants mentioned would be random as well.

So if the above is true, the markers aren't independent and they know it.

One addition: if you multiply 0.00005309 by 6,000,000, you get 318, which is the number of duplicate matches you can expect in the 6 million database. So, it's not really surprising that the Arizona lab did find a (near) match. Still, the chances of a false match for an individual are 0.00005309, so the question about its effectiveness/usefulness is: how many profiles are compared against the database per year?

If they can sufficiently suppress this story, they will have a lot less jurors quoting the news byte as absolute proof that DNA evidence can't be trusted.

And of course DNA can't be trusted without other corroborating evidence. If they find my hair in the car of somebody who turns up dead (or vice-versa) there's many orders of magnitude greater chance that one of us gave the other a ride than that one of us killed the other (unless I'm dead, in which case, fry her, please. KIDDING!)

I agree 100%. We see all the time stories about new evidence in death row cases. The first thing the prosecutor always argues is "he doesn't deserve a new trial, I stand by the conviction". If they truly cared about justice they'd say "hey we need to take another look at this". I don't know how they can live with that on their conscience anymore than I understand how defense lawyers can live with setting rapists and killers free on technicalities. I think the answer is that most lawyers in general lack a conscience, you'd have to to be successful.

I have seen first hand how the justice system truly works. Back in my youth I was a bit of a delinquent, and was convicted of many fairly petty crimes, mostly misdemeanor but nothing worse than a gross misdemeanor. I freely admit that I was usually guilty as charged, and I took my licks, but there were two cases where I was absolutely innocent.

Part of their strategy is to charge you with everything in the book, that way when plea bargaining comes around they can act like they are doing you a favor by dropping the extraneous charges if you plead to the main charge. The prosecutor had absolutely no interest in justice and wasn't interested in explanations or evidence, it was made very clear that if I refused to plead guilty it was going to cost me. In retrospect i'm confident I would have won both cases had I gone to trial, but the scare tactics can be quite effective, especially on a 20 year old kid.

I accepted the plea bargain in both cases to stay out of jail and avoid a costly trial and missing more work. Being innocent is just as costly as being guilty. Ironically I had to tell the judge under oath that I was really guilty and wasn't just saying so for the sake of the plea bargain. The convictions went on my permanent record and I got some hefty fines and probation, and the prosecutor got 2 more notches on her holster. 8 years later these convictions in particular, which were gross misdemeanors, cost me a very nice job.

Like I said, it was fairly petty and doesn't compare with the innocent people who are rotting in prison right now, but I can definitely sympathize. We see it all the time, people pleading guilty to avoid the death penalty or long prison sentences. When it is more of a punishment to prove your innocence than it is to plead guilty, something is wrong with the system.

"If they truly cared about justice they'd say "hey we need to take another look at this". I don't know how they can live with that on their conscience anymore than I understand how defense lawyers can live with setting rapists and killers free on technicalities."

There's a difference. A prosecutor in the situation you give is placing his own career interests above the interests of justice and the law.

A defense lawyer getting someone off "on a technicality" is at the very least demonstrating an allegiance to the letter of the law and a commitment to see that all people are treated under the law equally... and often may be the last line of defense against a government bent on violating civil rights.

There's really no such thing as "getting off on a technicality." Whenever you hear that phrase it's coming from a prosecutor or police officer who at the least didn't do their job properly and at worst violated the law themselves, and got caught.

When the police searched you illegally, you "got off on a technicality."When they came into your home without a warrant, you "got off on a technicality."When they didn't properly document and control the chain of possession of evidence used to convict you, thus throwing into doubt whether it's even legitimate evidence, you "got off on a technicality."When they interrogated you improperly or otherwise throw into question the accuracy of what they claim is your testimony to police, you "got off on a technicality."When they selectively show your photo to or otherwise lead the victim into presupposing you are the guy who did it, you "got off on a technicality."When the prosecutor has withheld information that might have exonerated you or changed a jury's verdict, you "got off on a technicality."

"If they truly cared about justice they'd say "hey we need to take another look at this". I don't know how they can live with that on their conscience anymore than I understand how defense lawyers can live with setting rapists and killers free on technicalities."

There's a difference. A prosecutor in the situation you give is placing his own career interests above the interests of justice and the law.

No, no, no. Three words explain why the prosecutor doesn't want to re-try the case and why this is the right thing to do in the circumstances: adversarial justice system.

It may not be the best system, but it's what we have; it is the duty of the prosecution to assume that they are right, just as it is the duty of the defence to assume that the prosecution is wrong. To allow the prosecutor to pick and choose the circumstances in which to present a strong case vs the circumstances in which to side with the defence introduces more bias into the system. Each side must present their case as if it was absolutely the way that they say it is, and then the jury must weigh the circumstances and decide.

No, no, no. Three words explain why the prosecutor doesn't want to re-try the case and why this is the right thing to do in the circumstances: adversarial justice system.
That makes sense if it's a difference of opinion over the validity of evidence or whatever>

The situations I'm talking about are not those. A prosecutor that withholds evidence he knows may be exculpatory is not a prosecutor assuming he is right - that's a prosecutor being corrupt.

The examples I gave are not examples of the adversarial justice system.

They are examples of civil rights violations. They are examples of unethical behavior. They are examples of government corruption. They are examples of crimes.

A prosecutor fighting retrial over a disagreement over the validity of evidence is an example of the adversarial justice system.

A prosecutor fighting retrial over evidence they improperly and knowingly withheld is not - it's an example of a criminal trying to cover up his crime.

Prosecutors and police are not always simply motivated by doing their jobs properly. They, like other people, are also motivated by greed, personal ambition, prejudice, personality flaws.

I think the answer is that most lawyers in general lack a conscience, you'd have to to be successful.

Disclaimer: my bar exam is a week from Tuesday.
I've had this conversation with people before, its why I want to stay out of criminal work. I guess the theory is that you throw everything on the table and hope that the opposing attorney is doing their job. That's the adversarial system. The Constitution dictates that the prosecution has to throw a lot more on the table. Ethics rules dictate that the prosecution also has to defeat their own case when they have information that will damage it. The defense attorney just has to do the best he can with the facts he is given.

Its easy to malign both sides of the system. However, neither is an easy task. The prosecution is ethically responsible for both society's interest, and to some extant, the defendant's as well. The defense attorney is responsible for the defendant's interest but, to a broader extent, society's interests as well. Defense attorneys protect even you and me in the sense that those accused of crimes, whether innocent or guilty, set the periphery of our legal protections. Guilty people have been responsible for the liberties you and I enjoy because they challenged the procedure, actions, and level of proof employed by the government. Whether or not an attorney is scum or devoid of conscience, there is an attorney on the other side taking them to task. Sure its an imperfect system, but its the best society can come up with and we muddle through.

Renaming basic human rights and due process, i.e. Rights of the Innocent, to some special "needs" category plays into special interest. Much like how "victim rights" laws throw to the wind fair court cases; the defense has their name thrown in multitude of papers and intense scrutiny, while the victim hides in anonymity. This has resulted in inequities in handling of cases--this become hugely apparant in both the Duke rape case and the Kobe Bryant rape case; consider these were big name cases where the flaws were apparant and utilized by the prosecution. (If you're wondering what should happen--if the victim's name is protectd in a case, the defense's name should also be protected in the case.)

Furthermore, such new terminology often is at some point redefined and abused--most of the citizens of the United States still don't realize that "violent" offenses constitute mere drug use or sex (so called statutory rape) under the 1984 Bail Reform Act (this is why California's 3 strikes laws ends up taking in so many repeat offenders). I can easily see "rights of the innocent" laws being ineffective and creating a special class as one-time DUI offenders now accused of murder get denied a "special class" of rights.

The facts are rather simple--for the past 60 years, laws have gone overly pro-prosecution. Part of this is government keepign score, as someone else put it. Part of this is also on the general public for being stupid, scared, and greedy--why people will look less horrified at a murderer than a pet killer, or if they see someone shackled they presume guilt, or see some sick social advantage in another person being locked up (prison doors open as the economy tanks means more jobs for the "innocent" sort of thinking).

DNA and fingerprints are useful in conjunction with other evidence, just as any other type of forensic or circumstantial evidence is. If someone passed out and died during a movie from a blow dart, for example, it would not be prudent to arrest a random person if they had tickets to the movie; similarly, if there is a particular DNA profile on the dart that 10,000 people match, those 10K should not be brought in. However, if someone had tickets to the movie && matched the DNA it would probably be a good idea to bring them in. CSI type shows are partly to blame - the average citizen on the jury trusts scientific evidence on its own far too much instead of the old detective story trio of means, motive and opportunity (forensics cannot help at all with the second).

If someone passed out and died during a movie from a blow dart, for example, it would not be prudent to arrest a random person if they had tickets to the movie; similarly, if there is a particular DNA profile on the dart that 10,000 people match, those 10K should not be brought in.

This is extraordinarily insightful. By the same logic, one can condemn the "no fly" potential terrorist list, which has in fact, caught no one and was no doubt accumulated in a similar fashion.

Very true. When's the last time you saw any kind of cop show, where they admitted to have screwed up? I can only remember it being done in Numb3ers in two episodes. One and a half actually, because only one of the shows talked about the fingerprints being misidentifed and the wrong guy being thrown in jail. The other was just a wrong assumption on their parts resulting in a manhunt.

Hell, I'd love for a show like 24 to have Jack Bauer or whomever torture the wrong guy for ho

No, it's not wrong. There are over 5 million profiles in the national database. Any slashdot reader should be able to work out how many pairwise comparisons are made when a database that size is searched against itself, and what the expected number of hits is when the match probability is about 1 in 100 billion.

This story is old news, and simply illustrates why we use 13 loci (average match probability around 1 in a quadrillion or less) and not 9. There has not been a 13-locus match between unrelated people

Since you're an expert on everything, why, then is the FBI blocking the attempts to study this? If they honestly believed the chances were that remote, they would be SPONSORING the fucking study, to PROVE they were right all along.
What they're doing is an admission of guilt to anyone with three brain cells.

Even though the odds of sharing a birthday with a random person are about 1/365, if you have 23 people in a room, you are likely to have at least one "birthday" match. With about 60 people, it's almost a certainty.

A back-of-the-envelope calculation gives me about half a million as the number of DNA samples required to give a 50/50 chance of having two people with matching DNA samples... but I might have messed up on that.

Why would they (law enforcement) not want there to be some doubt to DNA results? They're also being used to overturn old convictions.
In the case of current investigations, there is also other information (fingerprints, etc.) to help match a suspect to a crime...

From the description, this seems like an example of the birthday problem [wikipedia.org]. Briefly, in a group of 23 people the odds are 50-50 that two of them will have the same birthday, while in a group of 57 the odds are better than 99%. However, the odds that someone in the first group will share *your* birthday are far less, roughly 6.1%. Quoting the Wikipedia article, "For a greater than 50% chance that one person in a roomful of n people has the same birthday as you, n would need to be at least 253. Note that this number is significantly higher than 365/2 = 182.5: the reason is that it is likely that there are some birthday matches among the other people in the room."

Likewise, the odds of there being two people with matching DNA in a database are far higher than the odds of someone else matching *your* DNA. So it seems possible that the FBI could be quoting accurate odds, while at the same time there being lots of matches within the database.

So it seems possible that the FBI could be quoting accurate odds, while at the same time there being lots of matches within the database.

The odds might be technically accurate, but are they the correct odds for the FBI to be selling?

If a typical situation is having a suspect already in custody and then having the authorities run the suspect's DNA against a sample found at the crime scene, 110 billion is probably fair enough. If the authorities find some DNA and fish through the system for someone who matches, 110 billion is meaningless.

The odds might be technically accurate, but are they the correct odds for the FBI to be selling?

If a typical situation is having a suspect already in custody and then having the authorities run the suspect's DNA against a sample found at the crime scene, 110 billion is probably fair enough. If the authorities find some DNA and fish through the system for someone who matches, 110 billion is meaningless.

Well, let's rephrase it as the birthday problem. Someone in a classroom left a tack on the teacher's chair. Unfortunately, the tack was originally the prize in some stupid contest and for some reason claims to list its owner's birthday.

If there is someone you already suspect and their birthday matches, that's great. On the other hand, if there's only 23 people in the class and one has the same birthday as is shown on the tack, how sure are you that you've got the right person? Finally, if two people in

You are probably correct, but fundamentally there are several questions here that that does not answer: First, is it ethical - or even legal - to withhold evidence from the defense? Essentially, if the defense cannot question the validity of the prosecution's match, then that is what the FBI is doing.

Secondly, if the frequency of matches is such as to raise questions, should the FBI be gathering more detailed genetic information? If you do the birthday problem again, but this time instead of matching the sa

That would be fair enough, except for this: The FBI has tried to block distribution of the Arizona results and is blocking people from performing similar searches using CODIS. If this is correct, then the FBI does not have confidence in its own claims, which is worrisome. If they had confidence, they would have no need to block distribution of anything, indeed they would increase confidence in the system by having others validate that the probability of a false match is staggeringly low. I do not trust thos

As an American once arrested by the SS/FBI for computer related crime a while ago, DNA testing always worried me. I can understand it for violent offenders (which is how it was started and then carried over to all felons).

I can also tell you, if you refuse to submit to testing, they give you what they call "diesel therapy," taking you away from the cushy club fed camp you were in and busing you around the system until you relent. If you were given a half way house sentence or probation, they can revoke either for not submitting a sample.

Dispite turning my life around, finishing my degree and now working as a developer for a medium-size firm, I worry at times that one night I'll be hauled away because some flunky at the FBI mixed up DNA samples or didn't compare them correctly. I can imagine this being a horror scenario for anyone who's never broken the law, but can anyone imagine there being even a slight chance a bunch of narrow minded, non-technical cops are going to believe me, even if the crime is something totally unrelated to my history?

The LA Times says dozens of similar matches have been found. I have learned not to trust the media when they use questionable terms like "similar." By similar did they mean that in all of those other cases, 9 (or more) of the 13 genetic markers used were matched like they were in this one case? Or is the paper trying to make it seem more severe by saying dozens of similar instances exist, but these cases only match a couple of the marker--not nine markers. While this one example throws some questions into things, I want some more numbers before I start wasting a lot of money redoing every DNA test. Things such as scandal and fear sell papers. Using words such as similar allow writers to make things sound much worse than they might be. This sells papers.

The FBI says that the chance of any given person matching another unrelated person is 1 in 113 billion. They claim that the reason the Arizona lab tech found as many matches as she did ("dozens") is because she was checking the whole database (6 million entries) against itself. This is a straightforward birthday paradox issue, then.
According to the Wikipedia birthday problem page, the number of collisions expected given d= 113 billion different "birthdays" and n = 6 million "people in the room" is n - d + d((d-1/d)^n). This is about 160 matches! So in fact the FBI may be right.
Note that the chance of a given person matching _anyone_ in the database is about 0.0053%, which is much greater than 1 in 113 billion.

The FBI says that the chance of any given person matching another unrelated person is 1 in 113 billion. They claim that the reason the Arizona lab tech found as many matches as she did ("dozens") is because she was checking the whole database (6 million entries) against itself. This is a straightforward birthday paradox issue, then.

According to the Wikipedia birthday problem page, the number of collisions expected given d= 113 billion different "birthdays" and n = 6 mi

I think the really cool thing about this whole story is what it says about "race". For hundreds, if not thousands of years, and even now, people have using "race" and skin colour as reasons for subjugation. But here we have the first cast of extremely close matching DNA, 1 in 113 billion, and they are from different "races". Wow.

This, if anything, should dispel any stupid theories about the difference of "race" within the human species.

Only if you assume that "race" is an entirely genetic category, and not a product of culture and surrounds.

Also, these tests only check (I believe) up to 13 specific sequences. These sequences are the ones most likely to be different between individuals - they're not going to use the sequences for stuff like skin colour, because those would have large number of individuals with the same sequence.

If you match someone else on these tests, it means that you have a certain number of highly-variable sequence

Am I the only one who things the information about the characteristics of DNA evidence isn't understood as well as it could be? For example, ever notice how 20 years later or so a convicted murder can be cleared because of new DNA evidence that doesn't match the DNA of the killer? Has anyone done an experiment to see how DNA evidence could possibly change over the course of 20+ years?

Not to troll, but law enforcement agencies are really more interested in convictions than the truth. For instance, Virginia has a law that places a 21-day time limit on new evidence that can be used to exonerate someone wrongly convicted. I'm sure the FBI doesn't want it's coveted CODIS database subject to any doubt.

Remember the "birthday problem"?
"How likely do you think it is that any two people in this classroom have the same birthday?"
Most of the kids take a quick look around, see ~30 people in the room, know there's 365 days in a year and think--not very likely.
But there's usually a match.
In a classroom full of kids, the probability that any two children have the same birthday is (we'll ignore leap year for simplicity) 1/365.
We need to know the probability that none of the kids have the same birthday.
The probability of there being no collisions between two kids is still 1/365--this is just a more useful wording of the criterion.
So, first 2 kids, probability of a collision: 1/365
Third kid--if his b-day lands on either of the first two kids' you get a hit: 2/365
Fourth--3/365 chance of a collision....
And, of course, if you had 366 kids in the room, the last one's a sure thing.
You multiply the probabilities a series of independant events to get the probability of the whole series.
If we have 30 kids and 365 days, we want to know the chances of 30 misses (no collisions) in a row.
If P is the probability of something happening, then probability of NOT (something happening) is 1-P
So, probability of 30 misses in a row will be 1-(1/365) * 1-(2/365) * 1-(3/365) *... * 1-(30/365).
Which is ~.2703.
So, 1-.2703 tells you that if you've got 30 kids in the room you've got nearly a 3/4 shot at two of them having the same birthday.
Quickly iterating through the same process in oo.o calc for an FBI database with......ability to recognize 113E+09 unique DNA profiles...DNA from a million folks (no idea how many of us they really have)
gives you.988 probability of collision.
BTW, the general formula for the "birthday problem" is written as follows:
P=d!/[(d-n)!(d^n)]
Where
P=probability of no collisions
d=number of days in the year
n=number of students in the sample

> The FBI estimated the odds of unrelated people sharing those genetic markers to be as remote as 1 in 113 billion

As I've said time and time again. Forensic science is a scam. Second rate statisticians and second rate politicians team up with second rate scientists and second rate TV shows to convince the public that forensic superheroes can detect evidence of any evil crime you commit. It's just a way to keep the people under control.

if that's true why bother suppressing it and just let the do the comparisons. It'd be easy enough to bury them in regular scientific testing since the database would show that the hypothesis of these researchers is blatantly wrong and the only time being wasted is their time and not the FBI's.

There has never yet been a 13-locus match seen between unrelated people in the national database- despite the 5 million or so profiles currently in it. I'm sure the average Slashdot reader can manage to work out how many pairwise comparisons that is. (Hint- it's a pretty fucking big number.)

Well it seems that your statement of 'never' is simply because that comparison has not been run, since the FBI is doing everything possible to prevent testing of that theory. If its so unimaginably rare, it would seem that the FBI would be all for doing these searches to bolster the value of their evidence. However the results in MD would seem to challenge that dogma.

A 9-locus match between unrelated people is not surprising. That's why we don't sue only 9 loci, idiots!

Well it seems that California prosecutors are idiots and were using a 9 locus match to prosecute a man for a 2 decade old murder. From TFA: "Its implications became clear as she prepared to defend a client accused of a 20-year-old rape and murder. A database search had found a nine-locus match between his DNA profile and semen found in the victim's body. Based on FBI estimates, the prosecutor said the odds of a coincidental match were as remote as 1 in 108 trillion." So just to explain why we 'idiots' would use a 9 locus match: DNA collected at a crime scene is not a complete genome. Often it is only fragments. You may not have a full 13 loci to check because the fragment you have would not cover all 13 loci. There is, however a statistical nicety here that you've completely side-stepped in your haste to call us morons (which TFA mentions). The likelihood of finding matches of 9 of the 9 you have in your genome fragment is far less than the likelihood of finding any two people in a database with 9 of any 9 of 13 loci that match.

I match 12 out of 12 Y-DNA markers with 9 other people who have had their DNA tested. Based on our last names, none of us are related.

I don't think you should be able to use blind searches of a DNA database as evidence, because it's too easy to get false positives. It's only useful evidence against someone you've already found by other means, or as a way to generate leads.